Captive toy airplane



June 18, 1957 J. BORTFELDT CAPT-IVE TOY AIRPLANE Filed Dec. 27, 1954 United States Patent CAPTIVE TOY AIRPLANE Jiirgen Bortfeldt, Lehrte, Hannover, Germany, assignor to K. Arnold & Co., Nurnberg, Germany Application December 27, 1954, Serial No. 477,755 Claims priority, application Germany December 31, 1953 6 Claims. (Cl. 46-77) The present invention relates to toys and, more parparticularly, to captive toys. Known toys of this type are driven through the intervention of a flexible shaft which is introduced into the toy from a side thereof for instance from the end of a wing if the toy is a toy airplane. Thus, for instance, with a heretofore known toy airplane having a wing ,spread from about 40 to 80 centimeters, a steel wire having a diameter of from 0.3 to 0.8 millimeter, preferably 0.5 millimeter, is employed as a flexible shaft which connects the driving member with a drive shaft arranged on or in the toy airplane. Such straight wire having a length of several yards and preferably made of spring steel has the drawback that it cannot be rolled together to a smaller diameter without permanent change in the shape thereof. However, the smallest twisting or buckling results in strong oscillations during the operation or rotation of the wire with the result that the flying ability of the toy airplane is greatly impeded.

It is, therefore, an object of the present invention to provide a captive toy which will overcome the above mentioned drawback.

It is another object of this invention to provide a captive toy with a flexible drive shaft which will be practically non-sensitive to twisting and will have a relatively great twist resistance.

Still another object of this invention consists in the provision of a captive toy with a flexible drive shaft which will yield a maximum of safety of operation and life.

It is still another object of this invention to provide a captive toy, particularly a toy airplane, which has great maneuverability and can be controlled similar to its lifesize counterpart.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings in which:

Fig. 1 is a diagrammatic side view of a toy airplane according to the present invention.

Fig. 2 diagrammatically illustrates the connecting point at one end of a wing between the flexible driving shaft and a shaft located in the wing and employed for conveying driving power to the propeller shaft, the arrangement being such that the toy will move in clockwise direction about the playing person.

Fig. 3 is a view similar to that of Fig. 2 but showing the corresponding design of the wing end in connection with the flexible drive shaft for a toy which is intended to move in anti-clockwise direction about the person playing with the toy.

Fig. 4 is a bottom view of the toy airplane shown in Fig. 1.

General arrangement According to the present invention the transmission means for transmitting the driving force of a driving device to the toy airplane is formed by a wire coil wound in the manner of a helical spring. A particularly favor,- able material for a wire coil according to the invention consists of highly resistant steel wire as it is used for instance for the manufacture of helical springs. Such steel wire coil is not only not sensitive against twisting but is not ruined even if it is occasionally stepped upon. The manufacture of such wire coil can be effected similar to that of helical springs. In this connection the helical coil is first wound so that the windings are very close to each other whereupon later by the playing person the coil is pulled out to the desired length. The very small spacing between the windings is preferably maintained at the ends of the coil in order to yield a favorable fastening possibility with the shafts of the driving device and the toy airplane respectively.

The direction of winding and the torsional stress of the flexible drive shaft according to the invention should furthermore be at a certain ratio with regard to each other in order to obtain a maximum in safety of operation and a maximum of life. T 0 this end, the direction of winding and the torsional stress are preferably so selected with regard to each other that the wire coil is subjected to turning together stress i. e. to' a stress tending to decrease the diameter of the coil and its length. This means for instance when employing a wire coil wound similar to a right-hand screw and when looking in the direction of power flow, a torsional stress should occur in counterclockwise direction, whereas when employing a wire coil wound corresponding to a left-hand screw, a torsional stress should occur in clockwise direction when looking in the direction of the flow of power. If the coil wire is subjected to such a stress, also during a longerperiod of operation no change of any consequence in the shape of the wire coil will occur. If perhaps a certain shortening in the length of thewire coil should occur during a longer period of operation, this can be made up again without difficulties by pulling out the wire coil to a small extent.

A further advantage of a wire coil wound and subjected to stress in the manner mentioned above, consists in that the wire coil will tighten itself at both ends which are to be connected with the respective shafts so that the flexible shaft will not accidentally detach itself from the respective shafts even if it is subjected to a greater pull.

Structural arrangement While the present invention will be described in connection with a toy airplane, it is, of course, to be understood that the invention is, by no means, limited to a toy airplane but may also be used in connection with other toys.

Referring now to the drawing in detail, the toy airplane illustrated therein may be driven either from one or from the other side of the airplane so that assuming a stationarily mounted driving device, the toy airplane will move either in clockwise direction or in counter-clockwise direction around the driving device or the person playing with the airplane. Fig. 2 shows the connection of the driving shaft with the airplane for clockwise movement of the airplane. To this end, one end of the flexible drive shaft 4 is connected with the adjacent end of a shaft 3 carried by and protruding beyond the adjacent wing 1. The shaft 3 is connected with the propeller shaft proper in any convenient manner, for instance as shown in the manner illustrated in Fig. 4. According to Fig. 2, the flexible drive shaft 4 is designed in the manner of a righthand screw. As will be seen from Fig. 2, the windings of the end 5 of the flexible shaft 4 which windings are connected to the shaft 3 are very close together, while the other portion of the flexible shaft 4 has its windings relatively widely spaced. The arrow 6 indicates the flight direction, whereas the arrow 7 indicates the torque conveyed by the flexible shaft to the toy airplane.

As will be easily understood, the flexible drive shaft will during operation thereof and during rotation of the propeller 30 continuously exert a torque upon the toy airplane which tends to turn the toy about its transverse axis. Depending on the flight direction of the toy airplane and the direction of rotation of the drive shaft 4, this torque can bring about an increase or a decrease of the angle of attack. According to the invention this torque is taken advantage of to bring about an effect similar to that of an elevator, in order to adjust the respective flying position with regard to the transverse axis of the airplane and thereby to obtain different flight levels. In this connection it has been found favorable to cause said torque to bring about an increase in the angle of attack of the toy airplane so that when increasing the drive, a greater pulling force will be exerted by the ,propeller while simultaneously an increase in the angle of attack is obtained. The airplane will thus climb when the drive is increased; vice versa the pulling force of the propeller and the angle of attack will decrease when the drive is reduced so that either a stable straight flight or a diving will occur.

It will also be evident from the drawing, that the torque exerted upon the toy airplane will subject the wire coil 4 to a turning together of the windings so that the narrowly wound end 5 of the wire coil will more tightly pull itself or connect itself to the adjacent end of the shaft 3. The other end of the wire coil 4 which is connected to a driving device of any standard type (not shown in the drawing) is designed in an analogous manner so that also here a tightening of the adjacent windings of the wire coil to the drive shaft of the driving device will occur in view of the exerted torque.

According to the arrangement shown in Fig. 3, the flying torque is reversed with regard to that of Fig. 2, in other words, the airplane will fly in counter-clockwise direction around the driving device as indicated by the arrow 8. In such an instance the wire coil is wound in the manner of a left-hand screw and also in this instance the narrowly wound end 11 of the flexible shaft 10 will tighten itself upon the adjacent end of the shaft 12. The arrow 9 indicates the torque exerted by the flexible shaft 10 upon the toy airplane.

It is, of course, to be understood that if desired a connection may be provided which would allow one to drive the airplane from either side thereof.

The maneuverability of the toy airplane can furthermore beincreased by making the toy airplane slightly top-heavy. 'In other words, the center of gravity of the airplane may be located somewhat ahead of the more or less stable center of lift. By such an arrangement the airplane can be caused at a favorable angle of attack and a medium drive to carry out a stablehorizontal flight and, 'when decreasing or stopping the drive, the airplane will be caused to carry out a more or less strong gliding flight, whereas at a particular increase in the drive, the airplane will climb as mentioned above. Thus, it is possible to control the toy airplane practically in the manner of a normal airplane by varying the drive and varying the elevator control. Small corrections may be effected by a more or less great preadjustment of the horizontal stabilizers and elevators. It will thus be clear that with the toy airplane according to the-present invention a number of flying maneuvers can be carried out similar to an actual airplane. Thus, with the toy airplane according to theinvention also a three-point landing can be carried out. To this end, it is merely necessary that shortly before touching the ground, the drive is again increased. The torque suddenly exerted by the flexible shaft upon the toy airplane will bring about the required increase in the angle'of attack.

In order to increase the stability of the toy airplane about the longitudinal axis thereof, it'has been suggested to provide that side of the airplane which is remote from the side connected to the flexible driving shaft, with a counter-weight or tomake the wing to whichthe flexible driving shaft is connected smaller than the other wing or to provide the wing having the flexible driving shaft connected thereto, with a greater angle of attack. Tests have proved that the toy airplane according to the present invention is non-sensitive with regard to the unilateral load caused by the drive of the flexible shaft and its connection to one wing. By means of a small increase in the angle of attack of the wing having the flexible drive shaft connected thereto, this torque, about the longitudinal axis of the airplane can be balanced without difficulties so that neither additional weights nor asymmetric wing shapes are required.

The driving effect is clearly illustrated in Figs. 1 and 4 by the various arrows. The arrow 13 in Fig. 1 indicates the torque exerted by the flexible driving shaft upon the toy airplane. The arrow 14 represents the resulting lift for a medium airplane position. The arrow 15 illustrates the weight of the toy airplane attacking at the center of gravity 17 of the toy airplane. The reference numeral 16 represents the center of lift. Due to the distance between the points 16 and 17, 'bothforces 14 and 15 exert a torque upon the toy airplane as a-result of which the toy airplane becomes more 'or less top-heavy. This torque is more or less balanced by the torque exerted by the flexible drive shaft upon the toy airplane as indicated by the arrow so that the toy airplane is controllable with regard to its altitude level.

In order to produce an outwardly directed aerodynamic force with a toy airplane it has been suggested to arrange the propeller shaft so that its front .end is directed outwardly or to preadjust .the side rudder toward the outside. It has also been suggested to produce such outwardly directed aerodynamic force with a toy airplane by an appropriate selection of the connecting point of the flexible drive shaft with the toy airplane, which outwardly directed aerodynamic force was supposed to maintain the flexible driving shaft in stretched-out position. As has been found, in the most favorable instance the flexible shaft was to be led into the toy airplane in the neighborhood of the transverseaxisof the .toyairplane, especially at the end of a wing and was to be connected with the intermediate shaft establishing the driving connection with the propeller shaft. In other words, the flexible shaft was to be arranged-in the axis about which the toy airplane turns at different angles .of attack. It has now been found according to the present invention that a particularly high stability of the airplane about the vertical axis can be obtained when the intermediate shaft which leads from the connecting point with the flexible shaft to the propeller shaft proper, and is coupled thereto preferably by a step-down transmission, is so arranged that .it forms an acute angle with the vertical plane of symmetry-to the wings. The pointof intersectionof the axis of theintermediate shaft with the longitudinal vertical plane of the toy airplane should lie in or ahead of the centerof gravityof the toyairplane. With reference to Fig. 4, the transverse axis about which the toy airplane will turn at different angles of attack is designated with the-reference numeral 18. In this instance the center of lift 16 is located in the point of intersection of the transverse axis 18andthe longitudinal axis 19. The-center of gravity-of the toy airplane isdesignated with the reference numeral 17 which center-of gravity is located a certain distance ahead of the centerof lift 16. Furthermore, Fig. 4 illustrates that the intermediate shaft 22 which establishes the driving connection from the flexible shaft 20 to the propeller shaft 21 is so arranged that the connecting point of the flexible shaft 20 with the intermediate shaft.22 is located in the direct vicinity of the transverse axis 18. As would also be visible from Fig. 4, the intermediate shaft'22 formsan acute angle 23 with the transverse axis 18 so that the point of intersection 24 of the axis of shaft 22 with the longitudinal axis 19 is locatecl'in the center of. gravity 17 or 's'till'better, as shown in the drawing is located ahead of the center of gravity 1?. From the above it will be clear that during its flight,

the toy airplane will assume such a position with regard to the vertical axis that this axis is located in or at the intermediate shaft in the extension of the flexible drive shaft so that the longitudinal axis of the airplane is turned outwardly by a small angle as a result of which a portion of the driving force exerted by the propeller will act as a pulling force upon the flexible drive shaft. Due to this location of the intermediate shaft extending from the wing tip to a point near the center of the toy airplane, likewise an outwardly directed aerodynamic force is exerted. Consequently the toy airplane can get along also with a propeller shaft which is symmetrically arranged in the central vertical plane of the airplane while the side rudder has a relatively small angle of deviation. Due to the centrifugal force occurring during the flight and attacking at the center of gravity, this outwardly directed torque is at least in part compensated for. Both torques acting upon the toy airplane with regard to the vertical axis will thus at a certain angular position about the vertical axis balance each other so that the resultant of the outwardly directed aerodynamic force and the likewise outwardly directed centrifugal force will maintain the drive shaft in stretched-out condition. With specific reference to Fig. 4, from the above it will be clear that the intermediate shaft 22 has the tendency to adjust itself in the direction of the stretched-out flexible shaft 20 so that also the toy airplane will assume a flight direction which corresponds to the arrow 25. In this way the propeller 26 has not only a component force in flight direction but also a component force in radial direction toward the outside with regard to the drive shafts 21 and 22. This outwardly directed aerodynamic force exerts a torque upon the toy airplane in approximately the plane of the propeller. This torque is entirely or partly compensated by the torque which is produced by the fact that the centrifugal force attacks at the center of gravity 17. Due to the position of the drive shaft 22 as suggested according to the present invention, the flexible drive shaft will not only be held in stretched-out position but also a stable position of the toy airplane about its vertical axis will be obtained.

In order to assure that, as long as the toy airplane is still on the ground, and no outwardly directed aerodynamic force or centrifugal force is effective, the flexible drive shaft is in stretched-out position; according to a further development of this invention the tail skid or front wheel is to be connected to the toy airplane so that it has an outwardly turned position. With such an arrangement, the toy airplane will already at the start of the drive move away from the playing person so that also in this instance the danger of a curling will be reduced. With specific reference to Fig. 4, it will be noted that the tail wheel 26 which is rotatably supported by the member 27 is turned outwardly to such an extent that while the airplane is rolling over the ground during the landing operation it will bring the airplane into a position in which the flexible drive shaft will be held in stretchedout position.

It is, of course, to be understood that the present invention is, by no means, limited to the particular construction shown in the drawings but also comprises any modifications within the scope of the appended claims.

What I claim is:

I. In combination with a captive toy airplane with a right wing and a left wing: a propeller shaft carried by said toy airplane and extending in longitudinal direction thereof, a transmission shaft carried by one of said wings and having its inner end arranged for driving connection with said propeller shaft, and a flexible shaft in the form of a wire coil having one end thereof arranged for driving connection with the outer end of said transmission shaft and having its other end arranged for driving connection with a drive motor remote from said toy air plane, the center of gravity of said toy airplane during its normal flight position being located ahead of the center of lift of said top airplane to thereby make said toy airplane slightly top heavy, and the rotational driving direction of said wire coil flexible shaft being such as to increase the angle of attack of said toy airplane in conformity with the torque conveyed through said flexible shaft upon said toy airplane.

2. In combination with a captive toy airplane with a right wing and a left wing: a propeller shaft carried by said toy airplane and extending in longitudinal direction thereof, a transmission shaft carried by said right wing and having its inner end arranged for driving connection with said propeller shaft, and a flexible shaft in the form of a wire coil having one end thereof arranged for driving connection with the outer end of said transmission shaft and having its other end arranged for driving connection with a drive motor remote from said toy airplane, the center of gravity of said toy airplane during its normal flight position being located ahead of the center of lift of said toy airplane to thereby make said toy airplane slightly top heavy, said wire coil being wound in the sense of direction of a right hand screw.

3. In combination with a captive toy airplane with a right wing and a left Wing: a propeller shaft carried by said toy airplane and extending in longitudinal direction thereof, a transmission shaft carried by said left wing and having its inner end arranged for driving connection with said propeller shaft, and a flexible shaft in the form of a Wire coil having one end thereof arranged for driving connection with the outer end of said transmission shaft and having its other end arranged for driving connection with a drive motor remote from said toy airplane, the center of gravity of said toy airplane during its normal flight position being located ahead of the center of lift of said toy airplane to thereby make said toy airplane slightly top heavy, said wire coil being wound in the sense of direction of a left hand screw.

4. In combination with a captive =toy airplane with two oppositely located wings and a landing Wheel near one end of the fuselage of said toy airplane: a propeller shaft carried by said toy airplane and extending in longitudinal direction thereof, a transmission shaft carried by one of said wings and having its inner end arranged for driving connection with said propeller shaft, a flexible shaft in the form of a wire coil having one end thereof arranged for driving connection with the outer end of said transmission shaft and having its other end arranged for driving connection with a drive motor remote from said toy airplane, the center of gravity of said toy airplane during its normal flight position being located ahead of the center of lift of said toy airplane to thereby make said toy airplane slightly top heavy, the rotational driving direction of said wire coil flexible shaft being such as to increase the angle of attack of said toy airplane in conformity with the torque conveyed through said flexible shaft upon said toy airplane, and supporting means connected to said fuselage and arranged to hold said landing wheel in an outwardly turned position so that the plane of said wheel forms an obtuse angle with the vertical plane through the longitudinal axis of said plane in horizontal flight condition thereof, said wheel in said angular position being spaced further from the wing carrying said transmission shaft than from the wing opposite thereto.

5. In combination with a captive toy airplane with a right wing and a left wing: a propeller shaft carried by said toy airplane and extending in longitudinal direction thereof, a transmission shaft carried by one of said wings and having its inner end arranged for driving connection with said propeller shaft, and a flexible shaft in the form of a high grade steel wire coil adapted to be pulled out into various lengths and having one end thereof arranged for driving connection with the outer end of said transmission shaft and having its other end arranged for driving connection with a drive motor remote from said "7 toy air-plane, the center of gravity of said toy airplane during its normal flight position being located ahead .of the center of lift of said toy airplane :to thereby make said to-y airplane slightly top-heavy, and the rotational driving direction of said Wire coil flexible shaft being such as to increase the angle of attack of said toy airplane in conformity with the torque conveyed through said fiexible shaft upon said toy airplane.

6. In combination with a captive toy airplane with a right wing and a left wing: a propeller shaft carried by said toy airplane and extending in longitudinal direction thereof, a transmission shaft carried by one of said wings and having its inner end arranged for driving connection with said propeller shaft, and a flexible shaft in the form of a vwire coil adapted to be pulled out into various lengths and having one end thereof arranged for driving connection with the outer end of said transmission shaft and having its other end arranged for driving connection with a drive motor remote from said .toy airplane, the direction of Winding of said Wire coil being :opposite to the driving direction of said motor to thereby cause the windings .of said flexible shaft to vary their diameter in response to a variation of the torque exerted by said drive motor .upon said flexible shaft, the center of gravity of said toyairplanelduring its normal flight position being located ahead of the center of lift of said toy airplane to thereby make .said toy airplane slightly top-heavy, and the rotational driving direction of said Wire coil flexible shaft being such as to increase the angle of attack of said toy airplane in conformity with the torque conveyed through said flexible shaft upon said toy airplane.

References Cited in the file of this patent UNITED STATES PATENTS 1,852,340 Vlahov Apr. 5, 1932 2,161,971 Muller June 13, 1939 2,303,965 Walker Dec. 1, 1942 2,611,213 Johnson et al. Sept. 23, 1952 FOREIGN PATENTS 662,274 Great Britain Dec. 5, 1951 

